The method for manufacturing a MOS field effect transistor (MOSFET) including a silicon carbide semiconductor has a problem that the double diffusion technique, which is one of self-alignment techniques for channel formation, cannot be used due to a small diffusion coefficient of a dopant in silicon carbide. Therefore, there are several conceivable methods for solving this problem.
For example, in Patent Document 1, a second ion implantation mask is formed on a side wall of a first ion implantation mask, and a channel region is formed in a self-alignment manner such that the channel length is identical to the film thickness of the second ion implantation mask.
In Patent Document 2, an opening of a first ion implantation mask is filled with a second ion implantation mask after the first ion implantation, and then the second ion implantation is performed with a part of the first ion implantation mask being open, whereby a second ion implanted region is formed in a self-alignment manner with a first ion implanted region.